The present invention relates to a charged particle beam apparatus.
In the related art, there is known an apparatus which picks up a sample piece which is prepared by irradiating a sample with a charged particle beam which is formed of electrons or ions, and which processes the sample piece into a shape suitable for various processes such as observation, analysis and measurement by a scanning electron microscope and a transmission electron microscope (for example, refer to JP-A-5-052721 and JP-A-2008-153239).
In the related art, there is known an apparatus which picks up a sample piece which is prepared by irradiating a sample with a focused ion beam using a needle installed inside the apparatus, and which uses an image (also referred to as an absorption current image or an inflow current image) from an ion beam current which flows into the needle for clarifying a tip position of the needle when processing the sample piece into a shape suitable for various processes such as observation, analysis and measurement by a scanning electron microscope, a transmission electron microscope, or the like (for example, refer to JP-A-2000-171364). In this apparatus, in a case in which the surface of the sample is a complicated shape such as a semiconductor device pattern, since it is often not possible to recognize the tip position of the needle due to the influence of the shape of the surface of the sample in a secondary electron image, it is possible to effectively use the absorption current image.
In the present specification, “sampling” refers to picking up a sample piece which is prepared by irradiating a sample with a charged particle beam and processing the sample piece into a shape suitable for various processes such as observation, analysis, and measurement. More specifically, “sampling” refers to relocating a sample piece which is formed from a sample by processing with a focused ion beam to a sample piece holder.
In the related art, it cannot be said that the technology which is capable of automatically sampling the sample piece is sufficiently realized.
Examples of causes of obstructing of the automatic and continuous repetition of the sampling include that it is not possible to automatically perform image recognition of the needle which is used for picking up and transporting the sample piece, and the tip of the needle being molded or the needle itself being exchanged accompanying a deformation of the tip of the needle, and the like.
The reason that image recognition of the needle may not be automatically performed is that in a case in which the tip position of the needle is checked using an electron beam, a needle tip member may not be distinguished from the background image in the secondary electron image (or the reflected electron image), and the image recognition of the tip of the needle may not be performed, an incorrect image may be extracted, or the image recognition process may be stopped.
When checking the tip position of the needle using the absorption current image of the charged particle beam, when the secondary electron yield of the needle tip material is close to 1, the tip of the needle may not be distinguished from the background image, and the tip of the needle may not be confirmed. For example, although it is possible to confirm a tungsten needle using an absorption current image, when a carbon deposition film remains at the tip of the tungsten needle, it is not possible to perform image recognition on the carbon deposition film in the absorption current image, and there is a case in which, where the tip of the remaining carbon deposition film is to be determined to be the tip of the needle, instead, since the carbon deposition film is not formed, the tip of the tungsten needle may be erroneously recognized as the true tip. In such a state, when the needle is caused to approach a delicate sample piece, where the needle is to be stopped directly before the sample piece, instead a residue of the carbon deposition film which remains at the tip of the needle collides with the delicate sample piece.
In this manner, it is not possible to cause the true tip of the needle which includes the carbon deposition film to move to a target position using the image. In the worst case, the needle collides with the sample piece and destroys the sample piece, causing a problem of losing a valuable sample. Due to the collision of the needle with the sample piece, the needle is deformed, and a state is assumed in which the needle must be exchanged. Such a situation inhibits the automatic and continuous repetition of the sampling which is the original purpose.